1. Field of the Invention
This invention is directed to a laser power and energy meter.
2. Prior Art Statement
Solid-state, gas, semiconductor and other types of lasers are extensively employed in industry for producing laser beams used in such wide ranging fields as machining, medicine and communications. In such applications, it is necessary to be able to accurately measure the power of the laser beam that is emitted by the laser.
For this purpose, there have been developed laser output meters which measure the laser beam output using some type of heat sensor such as a thermopile, calorimeter, or pyroelectric sensor. However, when such a meter is used to measure the laser output, it is first necessary to cause the laser beam to impinge accurately on the target surface of the light receiver of which the heat sensor (hereinafter referred to as "laser output sensor") constitutes a part.
This is very difficult unless some special measure is taken because the laser beam is, in the first place, a spatially transmitted wave and, moreover, is frequently a beam outside the visible range or a pulsating beam. In the conventional laser output meters, this problem has been coped with by using an arrangement such as shown in Figure 4.
In FIG. 4, reference numeral 10 denotes a conventional laser output meter. The laser beam L.sub.B to be measured enters a blind hole in a light receiver housing 15 from an opening at one end thereof and impinges on the target surface 11 of a laser output sensor 12 positioned at the bottom of the blind hole. The laser output sensor 12 converts the light energy received thereby into an appropriate quantity of electricity which is used to produce a reading corresponding to the laser beam output on an indicator 13. The light receiver housing 15 enclosing the aforesaid components is mounted on a two-dimensional transfer table 20 which comprises micrometers 21 and 22 enabling it to be moved with high resolution in the Z direction (height direction) and the X direction (perpendicularly to the direction of the laser beam, within a horizontal plane).
When measurement is to be conducted, the laser beam to be measured is directed into the opening of the light receiver housing 15 and the micrometers 21, 22 are operated to move the two-dimensional transfer table 20 and the light receiver housing 15 by fine increments in the Z and X directions while observing the reading on the indicator 13. The micrometers 21, 22 are stopped at the positions giving the largest reading, which is taken to represent the laser output. Alternatively, a positioning plug 14 having a mark 16 on its head surface is screwed into the opening of the light receiver housing 15, the laser beam L.sub.B is directed onto the positioning plug 14 and the micrometers 21, 22 are operated to position the mark 16 with respect to the laser beam by observing the light reflected from the positioning plug 14. The positioning plug 14 is then removed to allow the laser beam L.sub.B enter the opening of the light receiver housing 15 and the laser beam power is read from the indicator 13.
However, where the method of adjusting the micrometers 21, 22 to obtain the maximum reading on the indicator 13 is used with a laser output sensor 12 of the heat sensing type, it is not possible to obtain an accurate measurement since the time constant of such a sensor is as long as from a few to several seconds and this means that changes in the point of incidence of the laser beam are not immediately reflected in the output reading so that drift is introduced to reduce the accuracy. On the other hand, the method employing the positioning plug 14 relies on the human eye and is singularly unreliable since the accuracy obtainable depends almost wholly on the skill of the operator and will differ greatly from person to person. Moreover, it is a considerably dangerous method in that it can harm the eyes and, at any rate, is totally useless with a nonvisible or pulsating laser beam.